Wallboard consists of panel-like sections of large surface area, particularly, gypsum board or drywall, which are installed at a construction site to form interior walls and ceilings of a building. Open wallboard seams are formed between abutting sections of the wallboard that meet side-by-side or that meet at inside corners. The seams are covered and hidden by constructing finished wallboard joints. Additional seams can appear as cracks in the wallboard, which are repaired by constructing finished wallboard joints.
A wallboard joint is constructed, by applying a joint compound reinforced with a reinforcing tape to fill and cover an open wallboard seam. The joint compound is in the form of a shapeable slurry that fills the seam. The reinforcing tape is applied to extend across the filled seam, and to overlap the edge margins of the wallboard abutting the filled seam.
One form of reinforcing tape is installed, first, by applying a joint compound in a thin layer on the wallboard edge margins. The thin layer is used, before the joint compound dries, to affix the tape onto the wallboard.
Another form of reinforcing tape is an adhesive-backed tape that has a pressure sensitive adhesive that adheres the tape to the edge margins of the wallboard. The adhesive backed tape is porous, in that it has openings through its thickness for passage of the joint compound through the tape, whereby the joint compound can pass through and fill the wallboard seam under the tape.
The wallboard joint is further constructed by applying a thin layer of joint compound to imbed the reinforcing tape and hide the same from view. The edges of the joint compound extend beyond corresponding edges of the reinforcing tape. Further, the edges of the joint compound are tapered or feathered to blend smoothly with the wallboard surface. Thereby, the joint compound hides or camouflages the tape from visual detection as an abrupt bump on the wallboard. After the joint compound has air dried, the surface of the joint compound is lightly sanded to provide a finished wallboard seam with a relatively smooth surface that smoothly blends with the wallboard surface. At least a single layer of joint compound is applied to hide the reinforcing tape, and many times, a second layer is applied, after the first layer has dried, to touch up surface defects in the previous layer. After the joint compound has air dried, a light sanding is performed to further reduce surface roughness, which provides a surface suitable for a prime coat, paint and other surface finishes.
Some wallboard sections are manufactured with tapered edge margins. Thereby, wallboard joints constructed on the tapered edge margins have an effectively lower profile compared to joints constructed onto the flat, major surface areas of the wallboard. However, some wallboard sections have non-tapered edge margins, wherein edge margins are part of the flat, major surface areas of the wallboard. Such wallboard sections benefit from having low profile, wallboard joints that are less prominent than the high profile, wallboard joints constructed on tapered wallboard edges.
A low profile wallboard joint is advantageously reinforced by a low profile tape. The low profile tape must be porous for passage of joint compound to fill a wallboard seam under the tape. However, pores or openings through the tape tend to weaken the tape. To counteract a weakened tensile strength, the tape could be reinforced with reinforcing yarn. The yarn tensile strength of the yarn generally increases with yarn thickness, i.e. the cross sectional thickness. However, it would be desirable to have a yarn that is relatively thin. Then, a wallboard joint that imbeds and hides the tape could be formed with a low profile. However, reducing the yarn thickness would reduce the tensile strength of the yarn. Accordingly, a reduced yarn thickness in a low profile tape must have a tensile strength that adequately reinforces the joint compound.
Further, a reduced yarn thickness is susceptible to pull out from the joint compound. Over the passage of time, thermal cycling and wind load cycling may cause incremental pull out of the yarns from their affixed positions in the joint compound. Thus, a reduced thickness yarn must adequately resist pull out from the joint compound.
Accordingly, there is a need for a low profile reinforcing tape for a joint compound, the tape having both a low profile and multiple openings for passage of a joint compound. Further, the tape must have a tensile strength to reinforce the joint compound. Further, the tape must resist pull out from the joint compound. Further, the reinforcing tape must lie flatly against the wallboard to assume a low profile.